130 PM PST TUE DEC 11 2007 WEATHER SYNOPSIS FOR TUESDAY AND WEDNESDAY A broad upper ridge is indicated by the US GFS model to generally remain over the northeast Pacific Ocean until late in the week. This should mostly cause a west to northwest flow aloft over the Northwest. Some warm air in the ridge is causing higher freezing levels Tuesday morning in the soundings at Forks and Salem. So some warmer temperatures may be seen Tuesday at higher elevations mainly in the Olympics and west of the crest in the Cascades. I would expect that east winds would keep the lower Cascade passes cool however on Tuesday. A weak front should approach over the ridge Tuesday afternoon and move over the Northwest on Tuesday night. This should cause some light precipitation mainly in the Olympics by Tuesday afternoon and in the north to central Cascades Tuesday night with lowering snow levels. This front is ending up weaker than earlier indicated. A change should be seen in the Cascade passes early Wednesday to light west winds and milder temperatures. A relative break is indicated by the US GFS model Wednesday. Then another very weak front is indicated by the US GFS model to move over the ridge and brush the Northwest Wednesday night. This may cause some light precipitation again mainly in the Olympics and north to central Cascades Wednesday night at low snow levels. WEATHER FORECAST FOR TUESDAY AND WEDNESDAY * OLYMPICS- Tuesday afternoon: Increasing clouds. Tuesday evening: Light snow. Tuesday night: Light snow showers. Wednesday: Mostly cloudy. Wednesday night: Light snow showers. * WASHINGTON CASCADES NEAR AND WEST OF THE CREST-CASCADE PASSES, INCLUDING STEVENS, SNOQUALMIE AND WHITE PASSES- Tuesday afternoon: Increasing clouds. Tuesday night: Light snow mainly north to central part changing to light snow showers. Wednesday: Mostly cloudy north and partly cloudy south. Wednesday night: Light snow showers mainly north to central part. * EAST SLOPES WASHINGTON CASCADES- Tuesday afternoon: Increasing mid or high clouds. Tuesday evening and night: Light snow showers higher elevations mainly north to central part. Wednesday: Partly cloudy mainly north to central part. Wednesday night: Light snow showers possible higher elevations mainly north to central part. * MT HOOD AREA- Tuesday afternoon: Increasing high clouds. Tuesday evening and night: Further increasing clouds and chance of light snow showers. Wednesday: Partly cloudy. Wednesday night: Mostly cloudy with chance of light snow showers. SNOW LEVELS-CASCADE MTNS 4000 ft N, 6000 ft C, 7000 ft S Tue aft 3000 ft N, 5000 ft C, 6000 ft S Tue eve 1000 ft N, 1500 ft C, 2000 ft S Wed and Wed eve SNOW LEVELS-OLYMPIC MTNS 5000 ft Tue aft 4000 ft Tue eve 1500 ft Wed and Wed eve Cascade Snow/Freezing Levels refer to the northern Washington Cascades (N) through Mt Hood area (S). Central Washington Cascade snow levels (typically near Snoqualmie Pass) are normally midway between indicated N and S levels. Note that surface snow/freezing levels are common near the passes during easterly pass flow and may result in multiple snow/freezing levels. 24 HOUR FORECAST OF PRECIPITATION IN INCHES OF WATER EQUIVALENT ENDING AT 4AM WED THU * HURRICANE RIDGE LT .10 LT .10 * MT BAKER LT .25 LT .25 * WASHINGTON PASS LT .10 LT .10 * STEVENS PASS LT .10 LT .10 * SNOQUALMIE PASS LT .10 LT .10 * MISSION RIDGE 0 0 * CRYSTAL MTN LT .10 LT .10 * PARADISE LT .25 LT .10 * WHITE PASS LT .10 LT .10 * MT HOOD LT .10 LT .10 WINDS IN MILES PER HOUR (MPH) * CASCADE PASS LEVEL WINDS E 15-20 Tue aft E 10-15 Tue eve E 5-10 Tue night W 5-10 Wed and Wed eve * FREE WINDS AT 5000 FT SE-SW 10-20 Tue morn SW 10-20 Tue aft and eve W 10-20 Wed morn W-NW 10-20 Wed aft and eve * FREE WINDS AT 9000 FT W-NW 15-25 Tue morn SW 20-35 Tue aft and eve W 3-40 Wed morn NW 25-35 Wed aft and eve EXTENDED WEATHER SYNOPSIS FOR WEDNESDAY THROUGH FRIDAY The ridge is currently indicated to rebuild over the Northwest coastal waters during the Thursday to Friday morning period. There may enough moisture in the northwest flow to cause some light showers at times mainly in the Olympics and north Cascades. Computer model information seems inconsistent in the longer range. A weak or moderate front is now indicated to move through the ridge and over the Olympic and Cascades Friday afternoon and night. This should cause some moderate precipitation in the Olympics and north Cascades and some light precipitation in the south Cascades at low snow levels. A short wave ridge and surface high pressure is indicated to rebuild over the Northwest on Saturday. This should help to cause light snow showers to end Saturday morning. Partly cloudy conditions and increasing offshore surface flow might be seen Saturday afternoon and evening. EXTENDED FORECAST FOR WEDNESDAY THROUGH FRIDAY Thursday to Friday morning: Partly or mostly cloudy with some light showers at times mainly in the Olympics and north Cascades. Friday afternoon and night: Light to moderate snow. Saturday morning: Light snow showers ending Saturday morning. Saturday afternoon and evening: Partly cloudy. * SNOW LEVELS Sea level to 1000 ft N, 1-2000 ft C and S Wednesday and Thursday 500 to 1000 ft N, 15-3000 ft S early Friday 2-4000 ft N and C, 4-6000 ft S late Friday